Beverages and other comestibles are often processed and packaged on mechanized conveyor systems which are lubricated to reduce friction between the packaging and the load bearing surface of the conveyor. In the past, the lubricants commonly used on the load bearing surfaces of these conveyor systems typically contained fatty acid soaps as the active lubricating ingredient.
Moreover, at least in a bottling operation, it is highly desirable that a lubricant be efficacious in lubricating the tracks upon which the various types of containers translate i.e. cans, glass and PET articles. Fatty acid lubricants are efficacious in conjunction with any of these types of containers. Thus, the lubricants disclosed in the above-referred to patents are "universal" lubricants in their application to various beverage containers.
These fatty acid lubricants have in the past provided excellent lubricity. However, fatty acid lubricants are also known to form insoluble precipitates in the presence of calcium and magnesium cations commonly found in hard water. Water softeners and chemical chelating agents such as EDTA must be used with lubricants based on fatty acids to prevent formation of such precipitates. Failure to implement such measures generally results in the formation of a precipitate which may plug the spray nozzles used for applying the lubricant to the conveyor.
Antimicrobial agents are particularly useful for conveyor systems which may transport food substances. Spillage of beverage and other comestibles on the conveyor often results in the growth of bacteria, yeast and mold and may create a slime or soil which, in turn, hampers conveyor performance and may also detract from product purity and appearance. Antimicrobial agents are particularly useful for reducing slime formation in conveyor systems which may transport food substances.
Fatty acid based lubricants have been formulated with effective antimicrobial agents, however, the tendency to react with water hardness ions compromises the overall performance of the lubricant.
Jansen, U.S. Pat. No. 4,839,067 discloses a process for the maintenance of chain-type conveyor belts by treating the conveyor belt with an antimicrobial lubricant composition containing a lubricating amount of a neutralized C.sub.12-18 primary fatty amine. However, as noted in Jansen, the primary fatty acid amines tend to form a precipitate in the presence of anions such as SO.sub.4.sup.-2, PO.sub.4.sup.-3 and CO.sub.3.sup.-2, commonly found as impurities in water. The precipitate may plug spray nozzles and soil the surfaces of the conveyor system in much the same way as fatty acid soaps in the presence of water hardness.
Schmidt et al., U.S. Pat. No. 5,182,035 discloses aliphatic ether diamine acetates which are used in lubricant compositions in combination with alcoholic hydrotropes used to enhance physical stability.
Weber et al., U.S. Pat. No. 5,062,978 also discloses aqueous lubricant compositions based upon fatty alkyl amines which are useful in conveyor belt operations, especially in the transport of bottles.
Schapira, Published European Patent Application No. 0,533,552 A1 discloses lubricant compositions comprising branched saturated or unsaturated C.sub.6 to C.sub.21 alkyl ether amines and diamines. The lubricant compositions are useful in conveyor operations and may also comprise a surfactant, and alcohol solvent.
Even though primary fatty acid amines have been found to provide adequate lubricity and antimicrobial activity, their usefulness is limited because of the tendency to form precipitates in the presence of those anions commonly found in water.
Accordingly, a substantial need still exists for an antimicrobial conveyor lubricant which provides a combination of superior lubricity, tolerance for both anions and cations commonly found in the water used to dilute the lubricant formulation prior to application to the conveyor system, and non-reactivity in the presence of food spillage such as beer.